I. Field of the Invention
The present invention relates generally to the field of communication networks, and particularly to systems and methods for integrating portable cellular service with landline telephone service.
II. Description of the Related Art
A wide variety of options are available for enhancing home or office telephone systems. For example, constraints on mobility arising from the limited length of telephone cords can be overcome through the purchase a cordless telephone. This enables an increase in roaming range, which can be extended to a virtually unlimited extent through the additional purchase of a cellular telephone. However, the relatively higher cost for cellular air time creates an incentive to have a cordless telephone for home use and a cellular telephone for use outside of the home.
A cordless telephone system typically includes a portable cordless handset and a cordless base station connected to a telephone company phone system by telephone landlines. The cordless base station has an assigned landline telephone number that allows the user to place and receive calls using the cordless portable handset within a limited range of the cordless base station, such as in a home.
As mentioned above, wireless communication outside of the range of the cordless telephone system may also be provided via a cellular telephone system. A cellular telephone system typically includes portable subscriber stations and cellular base stations connected to the landline telephone system by way of one or more cellular switching networks. Each cellular subscriber unit has an assigned cellular telephone number that allows calls to be made and received throughout the area covered by base stations operated by the applicable service provider and its affiliated providers.
It has been found that difficulties tend to arise when a user frequently relocates between the nominal domains of the cordless and cellular telephone systems. For example, incoming calls routed through the cellular system may be missed when the user is at home, and incoming calls routed to the user's landline telephone number may be missed when the user is outside of the home.
Efforts to address these difficulties have been directed to the development of handsets capable of operating as standard cellular radiotelephones and also as cordless (or microcellular) telephones when within range of an associated cordless (or microcellular) base station. For example, U.S. Pat. No. 5,488,649, entitled "METHOD FOR VALIDATING A COMMUNICATION LINK", issued Jan. 30, 1996, describes a cordless communication system incorporating a portable cellular cordless ("PCC") radiotelephone. The PCC has the ability to communicate with a conventional cellular radiotelephone system, with a microcellular base station, or a cordless base station. The cordless communication system uses authorization and call routing equipment to provide call routing information to a telephone switching system disposed to automatically route calls between the cellular, microcellular, and cordless systems. In addition, U.S. Pat. No. 5,594,782, entitled "MULTIPLE MODE PERSONAL WIRELESS COMMUNICATION SYSTEM", issued Jan. 14, 1997, describes a system in which handsets automatically switch between a standard cellular telephone radiotelephone mode of operation and an enhanced cordless mode when within range of picocells located at customer-selected locations. Unfortunately, implementation of such "dual-mode" systems may often be impractical due to the relatively high cost of dual-mode handsets and the increased system complexity arising from the addition of specialized call routing equipment.
Another proposal to facilitate integration of wireless (e.g., cellular or PCS) and wireline communication networks involves utilization of a subscriber personal base station to originate a call to the wireless network when the subscriber's cellular/PCS device is within range of the of the personal base station. Such a technique is described in, for example, PCT Application Number PCT/US96/19879, which was published Jul. 3, 1997 under International Publication Number WO 97/24004, the disclosure of which is herein incorporated by this reference. Such proposals contemplate that the call originated by the personal base station results in the wireless network being instructed to route all cellular/PCS calls to the subscriber's landline phone number when the cellular/PCS device is detected as being within range of the personal base station. Specifically, the call originated by the personal base station is directed to a new network element at a mobile switching center that answers the call, collects the necessary information, emulates a visitors location register ("VLR") and originates a registration notification to a subscribers home location register ("HLR"). When registered, the call will result in the HLR querying the new network element or special VLR for re-routing information on all subsequent calls made to the subscriber's cellular number. The special VLR will respond to the HLR by re-routing such subsequent calls to the subscriber's landline telephone number.
One disadvantage of the foregoing proposal is the requirement that a user generally possess at least a personal base station, a landline telephone and a cellular telephone. If the user does not desire to, for example, continue to posses a landline telephone upon acquiring a personal base station, then when the user leaves the location which would otherwise be served by the landline telephone (e.g., the user's home) such location is left without telephone service. Accordingly, the user is required to purchase all three of the devices listed above or accept the consequences of having only intermittent phone service available at home or office locations. Moreover, the personal base stations currently being considered for development in connection with the foregoing proposal generally utilize a wireless communication link to obtain identification information concerning the subscriber's cellular/PCS device when such device is determined to be within radio range of the personal base station. This results in an appreciable increase in cost, since the personal base station is required to incorporate a dedicated radio transceiver simply for detecting and/or obtaining information from the subscriber's cellular/PCS device.
Thus there exists a need for a system capable of further improving integrated wireless and landline telephone service in a cost effective manner, and which preferably eliminates the need for acquisition of a separate landline telephone, personal base station, and cellular/PCS telephone.